Apparatus for finishing forming dies

ABSTRACT

A POWER TOOL FOR GRASPING HIGH MASS RECTANGULAR ABRASIVE STONES AND FOR OSCILLATING THE HIGH MASS ABRASIVE STONES IN STRAIGHT LINE INERTIA-BALANCED OPPOSITION.

Feb. 23, 1971 c; H. HAAS APPARATUS FOR FINISHING FORMING DIES Filed NOV.21, 1968 l N VENTOR.

Fig.3

CHARLES HAAS IAJVQM ATTORNEY United States Patent 3,564,778 APPARATUSFOR FINISHING FORMING DIES Charles H. Haas, Philadelphia, Pa., assignorto The Budd Company, Philadelphia, Pa., a corporation of PennsylvaniaFiled Nov. 21, 1968, Ser. No. 777,758 Int. Cl. B24b 23/00 U.S. Cl.51-170 1 Claim ABSTRACT OF THE DISCLOSURE A power tool for grasping highmass rectangular abrasive stones and for oscillating the high massabrasive stones in straight line inertia-balanced opposition.

BACKGROUND OF THE INVENTION It has been the general practice in the diemaking art to contour machine a rough casting and then finish the die byhand tools and hand operations. Only one of the several hand operationswas performed with the aid of a power tool. After the die surface isrough machined, the raised ridges or cusps are usually removed with ahand-held rotary grinder fitted with abrasive wheels and/ or abrasivecones. Rotary grinders are heavy and require that they be held andguided in a precise position relative to the die surface or else theycut below the desired finished surface of the die. Rotary grindingoperations are performed intermittently because of the need to visuallycheck the progress of the operation and the need for the operator torest.

Other types of power tools have been suggested for finishing dies, suchas rotary and oscillating abrasive carrier tools commonly employed inautomobile body sheet metal repair shops. In addition to requiringphysical exertion and skill of the operator, the abrasive carriers wearout rapidly. Abrasive carriers tend to clog and to lose grit whichcauses scratches on the Work piece. Abrasive carrier tools, such assanders, employ resilient pads as backing for the abrasive carrier whichconcentrates forces on isolated spots causing rapid wear to the abrasivecarrier as well as the workpiece, thus, limiting the usefulness ofsanders for accurate die finishing.

SUMMARY OF THE INVENTION Accordingly it is the principal object of thepresent invention to provide a novel power operated tool for finishingthe surfaces of metallic dies.

It is a primary object of the present invention to provide a poweroperated tool for finishing die surfaces which is supportable by the diesurface.

It is a further object of the present invention to provide a poweroperated tool with a pair of large mass abrasive stones oscillated indirection opposite to each other to neutralize inertia forces.

It is another object of the present invention to provide a novelclamping plate adapted to securely grasp and hold abrasive stones and torapidly and easily release them.

It is a general object of the present invention to provide a poweroperated die finishing tool which is operable by personnel of averageskill to perform grinding, rough stoning, finish stoning and polishingoperations having equal or superior quality results to those obtained byhighly skilled personnel performing the same operations by hand.

The above and other objects of the invention as well as its manyfeatures and advantages will be apparent from the following descriptionof the prefered embodiment, reference being made to the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of thepreferred embodiment of the invention.

3,564,778 Patented Feb. 23, 1971 DESCRIPTION OF THE PREFERRED EMBODIMENTPower tool 10 comprises a pneumatic head 12 having an air supply hose 14which feeds two opposed pistons (not shown) in the head whichreciprocate in opposed straight line action. Such heads are commerciallyavailable and have been employed to drive sanders and buffers. A slide16 or 18 is guided by and bears upon the bearing plate 20 is connectedto each piston. Actuation of the control valve (not shown) causes theair supply to move the pistons and their attached slides back and forthWhile the head 12 remains stationary. It is preferred that the pistonsalways move in opposite direction to each other to neutralize inertiaforces.

Shoe plates 22, 24 are connected to the slides 16, 18 by bolts 26 whichare accessible through apertures 28 in the clamping plate assemblies 30,32. Shoe plates 22, 24 are connected to the clamping plates assemblies30, 32 preferably by welding at 34.

Each clamping plate assembly 30, 32 comprise a bed plate 36 and a pairof fixed clamp bars 38, 40* attached along the edges of the bed plate.One fixed clamp bar 38 is undercut as at 42 to provide a firm grip onthe stone 44. On the side opposite the undercut fixed clamp bar isprovided an undercut movable clamp bar 46 slidably supported on the bedplate 36 by Allen head screws 48.

It will be understood that the stone 44 varies in width and is fittedinto the clamping plate assemblies when the movable clamp bar 46 isopen. After the stone is inserted, screws 50 treaded in the fixed clampbar 40 are first tightened to hold the stone, then screws 48, threadedin the movable clamp bar 46, are tightened to lock the movable bar inplace. Stepped-face-slots 52 are provided in bed plate 36 to guidescrews 48.

Finger shields 54, 56 are mounted on the head 12 to prevent the operatorfrom inserting his fingers in the opening between the plates and thestones. An air cleaning tube 58 may be provided which directs an airstream between the two stones, thus keeping the workpiece clean.

A comparison between the former and the new methods of making dies willbest explain the advantages of the present invention. Heretofore, afterthe rough casting was machined the high marks left by the cutting toolswere completely removed by rotary hand grinders employing abrasivewheels and/ or abrasive cones having a number 43 grit size. Care had tobe taken to avoid grinding any of the low areas or troughs left by thecutting tool. In the prior art method of hand finishing the forming die,a typical operation required successive hand stoning with threeditferent stones, such as numbers 46H, 461 and 601. In the typical priorart method, hand finishing was followed by hand polishing employing atleast two polishing stones having a grit or grain size approximatelynumbers and 120. If a very high polish was required, another handpolishing step with a stone having a grit number was employed.

The new method permits the rotary hand grinding operation to be effectedwith broad abrasive wheels and/ or cones and does not require that thecomplete cusps or raised area be removed. The grinding operation iscompleted and the finishing operation started by employing the novelapparatus fitted with open or porous hard stones, such as number 43K.Grinding stones of this coarseness are not employed in typical handfinishing operations.

It is possible to complete the finishing operation with one or twostones, such as 46H and 461, dispensing with formerly used 601 stone. Ifboth 46H and 461 stones are used, the resulting finish on the die iscomparable to a light or low polish. If a higher polish is desired, handpolishing With number '80 grit stone is recommended. A very high polishcan be obtained by subsequent hand polishing with number 120 and/or 150grit stone. Plastic molding dies are further polished with oil and 200to 400 grit compound and/ or jewelers rouge usually applied with arotary rag or buffing wheel.

It is conservatively estimated that the time required to finish aforming die after it has been contour machined is reduced by two-thirdson the average. The two pairs of stones on the powered apparatus coverone-third square foot; the largest practical hand stone covers onlyonetwelfth square foot or one fourth as much area as the poweredapparatus. The two pairs of stones on the powered apparatus are movedapproximately fifteen thousand feet per hour, Whereas a hand opeartor isdoing well to move the hand stone three hundred feet per hour.

The operator of the powered apparatus does not exert any force on thestones since the force is applied by the weight of the stones and theapparatus. The rapid inertiabalanced oscillating stones tend to float onthe workpiece or die.

Careful selection of the stones used for self-cleaning characteristicshas the additional adavntage that the stones tend to wear to the shapeor contour of the die, thus insuring uniform wear and more accuratefinishing operations.

Having explained the invention and its method of use it is apparent thatthe novel apparatus is capable of performing a grinding operation and afinishing operation with the same stone because the apparatus cutssmoother. Further, the apparatus is capable of performing a finishingopeartion and a polishing operation with the same stone because theapparatus cuts smoother and more accurate. The ability to cut smootherand more accurate with coarser stones has effetcively eliminated one ormore steps formerly required when the dies were hand stoned. It isapparent that many types and grades of stones may be attached to thenovel apparatus to better accomplish finishing operations as previouslyperformed in the prior art, but in addition thereto stones employed toperform 5 finishing opeartions have now been etxended in usefulness toperform grinding operations or polishing operations.

I claim: 1. An oscillating abrasive-stone apparatus comprising, a headhaving a fixed bearing plate and at least one horizontally movableslide,

a recessed plate connected to the slide for mounting abrasive stonesthereto, rectangularly shaped abrasive stones mounted on said plate,

a pair of fixed clamp bars connected to said plate, a movable clamp barmounted on said plate, one of said fixed clamp bars having a pluralityof bolts threaded therein and engageable with the movable clamp bar toclamp the abrasive stones between a fixed clamp bar and the movableclamp bar, and a plurality of bolts slidably guided in slots in theplate and threadably mounted in said movable clamp bar for lockingthemovable clamp bar to the plate. References Cited UNITED STATES PATENTS175,566 4/1876 Kepler 51170.3 871,143 11/1907 Prugh 51175 928,154 7/1909Prugh 51-175 1,840,108 1/1932 Kincaid 51-1703 1,873,011 8/1932 Modglin51170.3 2,328,613 9/1943 Burleigh 51---175 FOREIGNPATENTS 173,15512/1921 Great Britain 51-173 WILLIAM R. ARMSTRONG, Primary Examiner

